| Aluminum micro-channel flat tube is a critical part of automotive air-conditioning condenser. With the requirement of heat exchange efficiency becomes much higher, the more tube holes and thinner wall thickness is demand, thus the extrusion of the tube is more and more difficult. At present, the dimension of the aluminum micro-channel flat tube produced by a company in Chongqing is unstable, and the ribs are yielding. Based on this problem, this paper discusses the direct extruding process and the extrusion die of aluminum micro-channel flat tube, the main research is as follows:(1)This paper first analyze the material flow property during the direct extrusion process of aluminum micro-channel tubes by using the professional extruding software HyperXtrude, which is based on ALE algorithm. The result shows that non-uniform velocity of the cross section of the micro-channel tube is the main reason that lead ribs to yielding, and also find the upper mold core is overstressed.(2)Through the CCD experimental method, this paper study the influence of billet heating temperature, extrusion container heating temperature,die heating temperature and extruding speed on the mean square error of tube’s section velocity and the maximum stress of the mold, and fit their response surface model. Then, the study obtained the optimal parameters of the extrusion process by the response surface method,the optimal heating temperatures of the billet, extrusion container and the mold are 517.5℃,432.5℃ and 525℃,and the extruding speed is 1.1mm/s.(3)The paper found that the height of mandrel shoulder had an effect on the die stress during the forward extrusion of the aluminum micro-channel tube. With the increasing height of the mandrel shoulder, stress of mandrel decrease and stress of mandrel shoulder is increased. As a result, the study obtained that when increase the mandrel shoulder height from 1mm to 2mm, the maximum stress of the die decrease to 1143 MPa observably, and the risk of broken tooth decrease as well.(4)Come up with method of setting up a secondary weld chamber to decrease the velocity non-uniformity of the aluminum micro-channel tube cross section in the bearing outlet. Establish a mapping relationship between the secondary welding chamber and the mean square error of flat tube’s sectional velocity by BP neural network. Use genetic algorithm to optimize the secondary welding chamber and the optimal parameter Y(length of secondary welding chamber) is 0.85 mm, and X(height of secondary welding chamber)is 0.55 mm.(5)With the analysis of the simulation by HyperXtrude, the velocity mean square error of Y direction and Z direction in the bearing outlet decrease by76.9% and 19% respectively, and the max stress of extrusion die reduce to 1332 MPa through the optimization of process and die. The strain of aluminum micro-channel tube is lower and displacement is more homogeneous, which shows the optimization is obvious.(6) With the extrusion experiment of aluminum micro-channel tube, the experimental result fits well with the simulation result. Both the microstructure and mechanical property of the tube is satisfied with the requirements through the test. With the use of the finite element analysis software HyperXtrude, this article optimize the direct extruding process and die of aluminum micro-channel flat Tube. The study solved the problems encountered in the company’s practical production, which has a certain practical guiding significance. The response surface methodology, BP neural network and genetic algorithm used in this paper can be used for prediction, analysis and optimization in the other research too. |
PDF Full Text Request